fix(ship-receipt): a stacked carry ignores files the child's own earlier main merge brought in (GST-1214)

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

bin/gstack-ship-receipt

@@ -666,11 +666,16 @@ function cmdCarry(rest: string[], json: boolean): number {
     // receipt written against the base while stacked reviewed the parent's hunks too, and the squash moved them into the
     // base (GST-1199). A parent counts only when merging it into the current base changes no product path.
     const measure = (rangeBase: string) => {
-      const listed = [touchedPaths(repoRoot, rangeBase, from), touchedPaths(repoRoot, headBase, head)];
-      if (!listed[0] || !listed[1]) return `git could not list the paths the branch touched against ${base}; run /ship on ${head.slice(0, 12)}`;
-      const touched = new Set([...listed[0], ...listed[1]]);
-      const spec = productSpec(repoRoot, rules, from, head, { touched, sides: [[rangeBase, from], [headBase, head]], own: branchSides(repoRoot, baseRef, from, '') });
-      if (!spec) return `git diff ${from.slice(0, 12)} ${head.slice(0, 12)} failed`;
+      const listed = [touchedPaths(repoRoot, rangeBase, from), touchedPaths(repoRoot, headBase, head), rangeBase === fromBase ? new Set<string>() : touchedPaths(repoRoot, fromBase, from)];
+      if (!listed[0] || !listed[1] || !listed[2]) return `git could not list the paths the branch touched against ${base}; run /ship on ${head.slice(0, 12)}`;
+      // From a stack parent, a path whose reviewed content is the base's (an earlier base merge brought it in) is base
+      // context, not reviewed product, unless HEAD changed it against the base (GST-1214).
+      const baseMerged = rangeBase === fromBase ? [] : [...listed[0]].filter(p => !listed[2]!.has(p) && !listed[1]!.has(p));
+      const touched = new Set([...listed[0], ...listed[1]].filter(p => !baseMerged.includes(p)));
+      const found = productSpec(repoRoot, rules, from, head, { touched, sides: [[rangeBase, from], [headBase, head]], own: branchSides(repoRoot, baseRef, from, '') });
+      if (!found) return `git diff ${from.slice(0, 12)} ${head.slice(0, 12)} failed`;
+      const skip = baseMerged.map(p => `:(exclude,literal)${p}`);
+      const spec = { ...found, product: [...found.product, ...skip], tests: [...found.tests, ...skip] };
       const ids = [patchId(repoRoot, rangeBase, from, spec.product), patchId(repoRoot, headBase, head, spec.product)];
       for (const r of ids) if (typeof r !== 'string') return `git could not compute the product patch-id at one of the heads: ${r.error}`;
       return { rangeBase, touched, spec, productFrom: ids[0] as string, productHead: ids[1] as string };

docs/ship-policy.md

@@ -1535,7 +1535,10 @@ the reviewed range (the reviewed head excluded, at most 100 commits) whose
 product change the current base already holds: `git merge-tree` of that commit
 into the base changes no product path. A conflicted product path never counts,
 so a parent that never landed is never treated as one, even when the child's
-merge dropped its change. The comparison then runs from that commit: an equal
+merge dropped its change. The comparison then runs from that commit, leaving out
+every path whose content at the reviewed head is the base's (a base merge the
+child made before its receipt brought it in) unless HEAD changed it against the
+base (GST-1214): an equal
 patch-id carries with reason `stack parent <sha12> landed`, base context next
 to the child's unchanged hunks is `RECEIPT_CARRY_SCOPED_REVIEW`, and any other
 difference refuses with `RECEIPT_CARRY_PRODUCT_CHANGED`.

test/ship-receipt-carry-squash.test.ts

@@ -240,3 +240,54 @@ describe('carry after a stack parent squash-merges, receipt written against main
     expect(landedStackParent(repo.work, { rangeBase: fork, reviewed, currentBase: mainTip }, ['.', ':(exclude,glob)test/**'])).toBeNull();
   }, 60_000);
 });
+
+describe('carry after a stack parent lands, the child having merged main before its receipt (GST-1214)', () => {
+  /** main <- parent (lib/util.js) <- feature (lib/retry.js), which merges main (wiki/) once before its receipt is written against main. */
+  function mergedStack(repo: FixtureRepo): { parent: string; reviewed: string; body: string } {
+    repo.git('checkout', '-q', '-b', 'parent');
+    const parent = commit(repo, { 'lib/util.js': SUB }, 'parent: sub');
+    repo.git('push', '-q', 'origin', 'parent');
+    repo.git('checkout', '-q', 'feature');
+    repo.git('reset', '-q', '--hard', parent);
+    commit(repo, { 'lib/retry.js': RETRY4 }, 'child: four retries');
+    repo.git('checkout', '-q', 'main');
+    commit(repo, { 'wiki/a.md': '# a\n', 'wiki/b.md': '# b\n' }, 'main: wiki');
+    repo.git('push', '-q', 'origin', 'main');
+    repo.git('checkout', '-q', 'feature');
+    repo.git('merge', '-q', '--no-edit', 'origin/main');
+    const reviewed = repo.git('rev-parse', 'HEAD');
+    const body = path.join(repo.root, 'body.md');
+    const w = runBin(repo, 'gstack-ship-receipt', ['write', '--pr', '8', '--base', 'main', '--version', '1.0.0', '--session-kind', 'unattended', '--body', body]);
+    expect(w.status).toBe(EXIT.ok);
+    return { parent, reviewed, body };
+  }
+
+  // Value: protects=a stacked child that merged main before its receipt keeps it once the parent squash-lands and main is
+  // merged again (gstack-evals#178 refused on 20 wiki/ paths its first base merge brought in); fails_when=the range from the
+  // landed parent counts paths that hold main's content at the reviewed head; seam=none; no_claim=gh pr edit (--body stands in)
+  test('the child carries when only its earlier base merge separates the parent range from HEAD\'s diff against main', () => {
+    const repo = makeFixtureRepo(); repos.push(repo);
+    const { parent, reviewed, body } = mergedStack(repo);
+    landOnMain(repo, { 'lib/util.js': SUB });
+    const head = repo.git('rev-parse', 'HEAD');
+    const out = carry(repo, body);
+    expect(out.err).not.toContain('RECEIPT_CARRY_PRODUCT_CHANGED');
+    expect(out.status).toBe(EXIT.ok);
+    expect(out.out).toContain(`CARRY: carried from ${reviewed.slice(0, 12)} to ${head.slice(0, 12)}`);
+    expect(receiptIn(body).carry!.reason).toBe(`stack parent ${parent.slice(0, 12)} landed + base merge`);
+  }, 90_000);
+
+  // Value: protects=fail closed: an edit to a file the earlier base merge brought in is product and refuses; fails_when=every
+  // base-merged path drops out of both sides, the child's own edit included; seam=none; no_claim=-
+  test('an edit to a base-merged file after the receipt refuses with RECEIPT_CARRY_PRODUCT_CHANGED', () => {
+    const repo = makeFixtureRepo(); repos.push(repo);
+    const { reviewed, body } = mergedStack(repo);
+    landOnMain(repo, { 'lib/util.js': SUB });
+    commit(repo, { 'wiki/a.md': '# a, edited by the child\n' }, 'child: edit wiki');
+    const out = carry(repo, body);
+    expect(out.status).toBe(EXIT.refused);
+    expect(out.out).toContain('CARRY: refused (RECEIPT_CARRY_PRODUCT_CHANGED)');
+    expect(out.err).toContain('wiki/a.md');
+    expect(receiptIn(body).head).toBe(reviewed);
+  }, 90_000);
+});